WO2023166905A1 - Method for operating desalting device - Google Patents

Method for operating desalting device Download PDF

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Publication number
WO2023166905A1
WO2023166905A1 PCT/JP2023/003390 JP2023003390W WO2023166905A1 WO 2023166905 A1 WO2023166905 A1 WO 2023166905A1 JP 2023003390 W JP2023003390 W JP 2023003390W WO 2023166905 A1 WO2023166905 A1 WO 2023166905A1
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water
desalting
desalination
operating
dilute
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PCT/JP2023/003390
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French (fr)
Japanese (ja)
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一輝 石井
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栗田工業株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/12—Controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/58—Multistep processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Definitions

  • the present invention relates to a method of operating a desalting device, and more particularly to a method of operating a desalting device having a first desalting device and a second desalting device.
  • the saturation index generally refers to the logarithm of the value obtained by dividing the product of concentration and ionic strength of each ion species involved in scale formation by the solubility product.
  • the desalination unit is operated in such a range that the saturation index does not exceed zero.
  • the desalting apparatus is operated after suppressing the formation of scale, for example, by adding a scale inhibitor.
  • flushing refers to the operation of discharging water from the concentrated water discharge pipe to the outside of the system by opening the on-off valve of the concentrated water discharge pipe while the water supply pump continues to operate. Contamination blocking the membrane surface can be effectively washed away by passing water at a higher flow rate than during normal operation. Flushing is generally performed at a frequency of 1 to 10 times/day for 30 to 120 seconds/time. However, flushing for several minutes/time is not sufficient to restore the performance of the desalting apparatus, and cleaning with a cleaning liquid is inevitable.
  • Another method is to reverse the flow direction of the water to be treated in the module. According to this method, it becomes possible to easily remove the turbidity accumulated in the raw water spacer, thereby improving the stability of the desalination apparatus (Patent Documents 1 and 2).
  • Patent Documents 1 and 2 the number of valves required for reversing the flow is significantly increased, resulting in a significant increase in initial cost.
  • a valve fails, the valve cannot be switched, and the stability of the device is greatly impaired.
  • Patent Document 3 describes a method of washing scale by passing washing water with low concentrations of F ions, Al ions, and Na ions.
  • this method when the ratio between the standardized permeate amount (corrected permeate amount) calculated from the values of flow rate, pressure, and water temperature in the reverse osmosis membrane treatment process and the preset initial standardized permeate amount becomes a specified value , switch to flow of washing water.
  • this method cannot sufficiently recover the degraded performance of the desalting apparatus.
  • an object of the present invention is to provide a method of operating a desalting device that can prevent deterioration of the desalting performance of the desalting device.
  • a method for operating a desalting device is a method for operating a desalting device having a first desalting device and a second desalting device, comprising: The water to be treated is supplied to the first desalination device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to the second desalination device to obtain the second concentrated water. and a normal operation step of separating into a second demineralized water; and a dilute water passing operation step of passing dilute water having a concentration lower than that of the first concentrated water through the second desalting device before the corrected permeated water amount of the second desalting device decreases.
  • a plurality of the second desalting devices are installed in parallel, and while the normal operation step is being performed in the first desalting device and some of the second desalting devices, other The dilute water passing operation step is performed in the second desalination unit of the above.
  • a method for operating a desalting apparatus is a method for operating a desalting apparatus having a first desalting apparatus and two second desalting apparatuses, comprising: The water to be treated is supplied to the first desalting device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to one of the second desalting devices to obtain the second a first water flow pattern in which concentrated water and second desalted water are separated, and dilute water having a concentration lower than that of the first concentrated water is passed through the other second desalination device; The water to be treated is supplied to the first desalting device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to the other second desalting device to obtain the second a second water flow pattern in which concentrated water and second desalted water are separated, and dilute water having a concentration lower than that of the first concentrated water is passed through one of the second desalting devices; alternating between Switching between the first water flow pattern and the
  • water in which the concentration of dissolved salts is less than the saturated solubility is used as dilute water.
  • the desalinated water of the first desalting device or the first desalting device and the second desalting device is used as diluted water.
  • a scale inhibitor is added to diluted water.
  • the desalination device is a reverse osmosis membrane device.
  • the temperature of the dilute water is 25°C or higher.
  • the first concentrated water has a water temperature of 20° C. or higher, a pH of ⁇ 6.0, a calcium ion concentration of 50 to 500 mg/L, an aluminum ion concentration of 0.01 to 0.5 mg/L, Iron ion concentration: 0.01-0.25 mg/L, silica concentration: 500-1500 mg/L.
  • the water to be treated is passed through the first desalination apparatus to separate the first desalted water and the first concentrated water, and the first concentrated water is separated into the second
  • the water is passed through a desalting device to separate into a second desalted water and a second concentrated water.
  • Decrease in desalination performance of the second desalination device by passing dilute water through the second desalination device before the desalination performance of the second desalination device is substantially degraded by performing the normal operation step can be prevented.
  • the desalinated water of the first or second desalting device is used as dilute water when performing the flux recovery operation of the second desalting device, ancillary equipment such as a tank is unnecessary, and the device configuration is It becomes simple.
  • the attached scale of the second desalting device is sufficiently dissolved and removed as compared with the case where the water to be treated is used as the dilute water. be able to.
  • FIG. 3 is a flow chart explaining a method of operating the desalination apparatus according to the embodiment
  • FIG. 3 is a flow chart explaining a method of operating the desalination apparatus according to the embodiment
  • It is a flowchart explaining the operating method of the desalination apparatus of an Example.
  • It is a flowchart explaining the operating method of the desalination apparatus of an Example.
  • 4 is a graph showing the results of Examples and Comparative Examples.
  • a reverse osmosis membrane device (RO device) will be described as an example of a desalting device, but the present invention is not limited to this.
  • the reverse osmosis membrane an aromatic polyamide-based reverse osmosis membrane is suitable, but the reverse osmosis membrane is not limited to this.
  • desalting devices other than reverse osmosis membrane devices include nanofiltration membrane devices, forward osmosis membrane devices, membrane distillation devices, electrodialysis devices, and electrodeionization devices.
  • water to be treated include, but are not limited to, industrial water, well water, and fluorine-containing waste water having a salt concentration of about 10 to 5000 mg/L, particularly about 50 to 1000 mg/L.
  • FIGS. 1 and 2 show the configuration of a desalting device used in the desalting device operating method according to the embodiment.
  • the thick solid line indicates the flow of water during operation.
  • PI indicates a pressure sensor
  • FI indicates a flow sensor.
  • the first RO device 4 and the second RO device are installed in series.
  • two second RO devices 21 and 22 are installed in parallel.
  • one second RO device 21 is in normal operation and the other second RO device 22 is in lean water flow operation, and in FIG. The other second RO device 22 is operating normally.
  • the raw water in the raw water tank 1 is supplied to the first RO device 4 via the pump 2 and the pipe 3, and the desalinated water (permeated water) is passed through the pipe 31, the valve 32, and the pipe 33 as desalted water. taken out.
  • the concentrated water (first concentrated water) of the first RO device 4 is supplied to one second RO device 21 via pipes 34 and 35, valve 36, and pipe 37.
  • the desalted water (permeated water) of the second RO device 21 joins the pipe 33 via pipes 61 and 62 and is taken out as desalted water.
  • Condensed water in the second RO device 21 is taken out as concentrated water via a pipe 63 , a valve 64 , a pipe 65 , a valve 66 and a pipe 67 .
  • a pipe 38 branched from the pipe 34 is connected via a valve 39 and a pipe 40 to the water inlet of the second desalination device 22 on the other side.
  • the valve 39 is closed.
  • the pipes 31 and 37 are connected by a pipe 41 and a valve 42 . Further, the pipes 31 and 40 are connected by a pipe 43 and a valve 44 . In FIG. 1, valve 42 is closed and valve 44 is open. Therefore, part of the first desalted water in the pipe 31 is supplied to the water supply port of the second desalinator 22 through the pipes 43 and 40, and the second desalinator 22 is operated with dilute water.
  • the desalted water of the other second RO device 22 joins the pipe 33 via the pipes 73 and 62 and is taken out as desalted water.
  • the concentrated water from the second RO device 22 is returned to the raw water tank 1 via pipes 74, 77, a valve 78, and pipes 79, 71.
  • one of the second demineralizers 21 is operating with dilute water, and the other second demineralizer 22 is normally operating.
  • the raw water in the raw water tank 1 is supplied to the first RO device 4 via the pump 2 and the pipe 3, and the desalinated water (permeated water) is taken out as desalted water via the pipe 31, the valve 32, and the pipe 33.
  • the valve 36 is closed and the valve 39 is open. Therefore, the concentrated water (first concentrated water) of the first RO device 4 is supplied to the other second RO device 22 via pipes 34 and 38 , valve 39 and pipe 40 .
  • the desalted water (permeated water) of the second RO device 22 joins the pipe 33 via the pipes 73 and 62 and is taken out as desalted water. Condensed water from the second RO device 22 flows through pipes 74, 75 and valve 76 into pipe 65 and is taken out as concentrated water.
  • the valve 42 is open and the valve 44 is closed. Therefore, a part of the first desalted water in the pipe 31 is supplied to the water supply port of one of the second desalting devices 21 through the pipes 42 and 37, and the second desalting device 21 is operated with dilute water. .
  • the desalted water of the one second RO device 21 joins the pipe 33 via the pipes 61 and 62 and is taken out as desalted water.
  • the concentrated water of the one second RO device 21 is returned to the raw water tank 1 via the pipes 63, 68, the valve 69, and the pipes 70, 71.
  • one of the two second desalting devices 21 and 22 installed in parallel is normally operated while the other is passing the first desalted water.
  • one first RO device 4 is installed and a total of two second RO devices 21 and 22 are installed, but more may be installed each.
  • the diluted water is separated into concentrated water and desalinated water. (not shown) may be closed so that the diluted water is not separated into concentrated water and desalted water, and only the concentrated water is discharged from the second RO devices 21 and 22 .
  • the flow rate of dilute water can be appropriately determined according to the clogging state of the desalting device. is preferred. Specifically, it is preferably 300 to 2000 L/Hr per one 4-inch module, and 1.8 to 10 m 3 /Hr per one 8-inch module. Further, the pressure on the concentrated water discharge side of the desalting device is preferably 0.1 to 2 MPa.
  • one of the second RO devices is normally operated for a predetermined period of time and the other second RO device is operated with lean water, and then the one of the second RO devices is operated normally.
  • This predetermined time is exemplified by 10 to 240 minutes, especially 30 to 180 minutes, eg about 90 minutes.
  • the first desalted water is used as the dilute water, but in the present invention, the dissolved salts in the dilute water should be less than the saturation solubility. Therefore, the second desalted water (permeated water of the second RO device) may be used as diluted water. Further, a mixture of the permeated water of the first RO device or the second RO device and raw water may be used as diluted water. Furthermore, a mixture of the permeated water of the first RO device or the second RO device and the first concentrated water may be used as diluted water.
  • a scale inhibitor may be added to the dilute water. By adding a scale inhibitor, it is possible to obtain the effects of improving the dissolving power of scale and preventing reattachment of dissolved scale.
  • the scale inhibitor can be appropriately selected according to the type of desalination equipment used and the raw water.
  • a reverse osmosis membrane device is used as a desalination device, and in the case of water to be treated that produces calcium carbonate scale, phosphonic acid such as 2-phosphonobutane-1,2,4-tricarboxylic acid, acrylic acid and 2-acrylamide -Copolymer of 2-methylpropanesulfonic acid, polyacrylic acid, etc. can be used, and in the case of water to be treated that produces calcium fluoride scale, 2-phosphonobutane-1,2,4-tricarboxylic acid Phosphonic acid such as acid, polyacrylic acid, and the like can be used.
  • the amount of these scale inhibitors added is about 10 to 1000 mg/L.
  • a pH adjuster may be added to the dilute water to obtain the effects of improving the dissolving power of scale and preventing reattachment of dissolved scale.
  • the RO devices are installed in two stages in the above embodiment, they may be installed in three or more stages. When three or more stages are installed, it is preferable that the desalinator through which dilute water is passed is the one at the last stage.
  • the present invention can be suitably used when calcium fluoride scale or calcium carbonate scale is generated in the second RO device.
  • the first concentrated water supplied to the second RO device can be suitably used in the following cases.
  • Iron ion concentration 0.01 to 0.25 mg/L (preferably 0.1 to 0.25 mg/L)
  • Silica concentration 500-1500 mg/L (preferably 700-1200 mg/L)
  • the corrected permeation flux is generally calculated by the method described in the method for standardizing permeation water amount performance data of reverse osmosis membrane elements and modules as shown in JIS K 38021990.
  • the water permeation performance data is corrected by the following formula (1) to calculate the corrected permeation flux Fps .
  • Q pa amount of permeated water under actual operating conditions (m 3 /d)
  • P fa Operating pressure (kPa) under actual operating conditions
  • ⁇ P fba Module differential pressure (kPa) under actual operating conditions
  • P pa Permeate side pressure (kPa) under actual operating conditions
  • ⁇ fba Osmotic pressure (kPa) of the average solute concentration on the supply side and concentration side under actual operating conditions
  • TCF a Temperature conversion factor under actual operating conditions
  • P fs Operating pressure under standard operating conditions (kPa) ⁇ P fbs : Module differential pressure (kPa) under standard operating conditions
  • P ps Permeate side pressure (kPa) under standard operating conditions
  • ⁇ fbs Osmotic pressure (kPa) of average solute concentration on feed side and concentration side under standard operating conditions
  • TCF s Temperature conversion factor under standard operating conditions
  • Raw water in a raw water tank 81 can be sent through a pump 82 and a pipe 83 .
  • the pipe 83 branches into pipes 84 and 85 and is connected to first RO devices 86 and 87 .
  • Permeated water from the first RO devices 86 and 87 can be taken out as demineralized water via pipes 88 and 89 and a confluence pipe 90 .
  • the concentrated water from the first RO devices 86 and 87 is supplied to the second RO device 94 via the pipes 91 and 92 and the confluence pipe 93.
  • the permeated water of the second RO device 94 joins the pipe 90 from the pipe 95 .
  • Condensed water in the second RO device 94 is discharged outside the system through a pipe 96 .
  • the dilute water in the dilute water tank 97 can be supplied to the second RO device 94 via the pump 98, the pipe 99 and the pipe 93.
  • the above desalted water is used as diluted water.
  • Fig. 3 shows a normal raw water treatment operating state, in which the pump 82 is operating and the pump 98 is stopped.
  • the raw water is subjected to RO treatment by the first RO devices 86, 87 or the second RO device 94, and separated into permeated water (demineralized water) and concentrated water.
  • FIG. 4 shows a state in which dilute water is passed through the second RO device 94 .
  • the pump 82 is stopped, only the pump 98 is operated, and the raw water supply to the first RO devices 86 and 87 is stopped.
  • the dilute water in the dilute water tank 98 is passed through the second RO device 94 to dissolve and remove the scale of the second RO device 94 .
  • the permeated water is prevented from flowing out to the pipe 95 when dilute water is passed through the second RO device 94. However, when dilute water is passed through the second RO device 94, The permeated water may be allowed to flow out to the pipe 95 .
  • diluted water permeate water obtained by passing simulated raw water through an RO apparatus as shown in FIG. 3 was used. In addition, 10 mg/L of the above scale inhibitor was added.
  • Example 1 The simulated raw water and simulated dilute water were passed through the desalting apparatus shown in FIGS. 3 and 4 in the following order and under the following conditions.
  • Simulated raw water flow process (Fig. 3): Simulated raw water was passed so that the initial permeation flux was 0.45 m/D and the water flow rate was 0.1 m/s, and the operation was carried out for 90 minutes at a recovery rate of 73%. (Corrected permeate flux does not drop substantially at 90 minutes of operation.)
  • Dilute water flow process (Fig. 4): After performing the simulated raw water flow process for 90 minutes, dilute water is passed for 30 minutes at the same pressure and water flow rate as the simulated raw water flow process. After that, the process returns to the simulated raw water passing step in FIG.

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Abstract

This method operates a desalting device having a first desalting device and a second desalting device, the method involving: a normal operation step for supplying water to be treated to the first desalting device, separating the water to be treated into first concentrated water and first desalted water, supplying the first concentrated water to the second desalting device, and separating the first concentrated water into second concentrated water and second desalted water; and a dilute water passing operation step for passing dilute water having a concentration lower than the first concentrated water through the second desalting device before a corrected permeated water amount of the second desalting device decreases.

Description

脱塩装置の運転方法Operation method of desalting equipment
　本発明は、脱塩装置の運転方法に係り、特に第１脱塩装置と第２脱塩装置とを有する脱塩装置の運転方法に関する。 The present invention relates to a method of operating a desalting device, and more particularly to a method of operating a desalting device having a first desalting device and a second desalting device.
　逆浸透（ＲＯ）膜等の脱塩装置では、長期間の運転により炭酸カルシウム、シリカ、フッ化カルシウム等のスケールの析出や、有機物による膜閉塞が発生し、塩除去率の低下や透過水量の低下等の脱塩装置の性能低下をもたらす。スケール閉塞の場合、脱塩装置の性能低下を防ぐために原水中のイオン濃度を測定し、脱塩装置の濃縮水において飽和指数を超えないように運転する方法が採用される。ここで飽和指数とは、スケール生成に関与する各イオン種の濃度・イオン強度の積を溶解度積で割った値の対数値を一般的に指す。この飽和指数がゼロを超えないような範囲で脱塩装置を運転する。さらに飽和指数がゼロを超えるような場合においては、例えばスケール防止剤の添加によってスケールの生成を抑制し、脱塩装置を運転する。 In desalination equipment such as reverse osmosis (RO) membranes, long-term operation causes deposition of scales such as calcium carbonate, silica, and calcium fluoride, and membrane clogging due to organic matter, resulting in a decrease in salt removal rate and a decrease in the amount of permeated water. This leads to deterioration in the performance of the desalination device, such as deterioration. In the case of scale clogging, a method of measuring the ion concentration in the raw water and operating the concentrated water of the desalting device so as not to exceed the saturation index is adopted in order to prevent the performance of the desalting device from deteriorating. Here, the saturation index generally refers to the logarithm of the value obtained by dividing the product of concentration and ionic strength of each ion species involved in scale formation by the solubility product. The desalination unit is operated in such a range that the saturation index does not exceed zero. Furthermore, when the saturation index exceeds zero, the desalting apparatus is operated after suppressing the formation of scale, for example, by adding a scale inhibitor.
　スケール防止剤の添加によっても抑制不可能であるような飽和指数を大きく超える水質である場合、従来ではスケールを除去するために酸洗浄やアルカリ洗浄の薬品洗浄が行われてきた。しかし一般的な洗浄では、装置を止め、洗浄液で洗浄し、洗浄液を回収した後に通水を再開することから、洗浄コストが大きくなる。そこで、長期間運転しても脱塩装置の性能が低下することなく、薬品洗浄を必要としない脱塩装置の運用が望まれていた。 If the water quality greatly exceeds the saturation index, which cannot be suppressed even by adding scale inhibitors, conventionally, chemical cleaning such as acid cleaning and alkaline cleaning has been performed to remove scale. However, in general cleaning, the cleaning cost increases because the apparatus is stopped, the cleaning liquid is used, and the water supply is restarted after the cleaning liquid is recovered. Therefore, it has been desired to operate a desalting apparatus that does not require cleaning with chemicals without degrading the performance of the desalting apparatus even after long-term operation.
　脱塩装置の運転方法の一つとして、フラッシング法が挙げられる。ここでフラッシングとは、給水ポンプの稼働を継続したまま、濃縮水排出配管の開閉弁を開とすることにより、濃縮水排出配管から給水を系外へ排出させる操作を指す。通常運転時より速い流速で通水することにより、膜面を閉塞させる汚れを効果的に洗い流すことができる。フラッシングは、１～１０回／日の頻度で、３０～１２０秒／回で行うことが一般である。しかし、数分／回程度のフラッシングでは性能低下した脱塩装置を回復させることは不十分であり、結局洗浄液による洗浄を実施せざるをえない。またフラッシングを行う場合、濃縮水配管の開閉弁を開とすることから、フラッシングを行う間は、透過水の生産を行うことができず、脱塩装置の回収率は低下してしまう。
　さらに、ＲＯ給水相当の塩類濃度では、フラッシングによる性能低下した脱塩装置を回復させることは不十分であり、塩類濃度の低い水でフラッシングを行うことが望ましい。 One method of operating a desalinator is a flushing method. Here, flushing refers to the operation of discharging water from the concentrated water discharge pipe to the outside of the system by opening the on-off valve of the concentrated water discharge pipe while the water supply pump continues to operate. Contamination blocking the membrane surface can be effectively washed away by passing water at a higher flow rate than during normal operation. Flushing is generally performed at a frequency of 1 to 10 times/day for 30 to 120 seconds/time. However, flushing for several minutes/time is not sufficient to restore the performance of the desalting apparatus, and cleaning with a cleaning liquid is inevitable. In addition, since the on-off valve of the concentrated water pipe is opened when flushing is performed, permeated water cannot be produced during flushing, and the recovery rate of the desalting apparatus decreases.
Furthermore, the salt concentration equivalent to RO feed water is insufficient to restore the performance of the desalting apparatus whose performance has deteriorated due to flushing, and it is desirable to perform flushing with water having a low salt concentration.
　その他の方法として、モジュールの被処理水の流れ方向を反転させる方法がある。この方法によると、原水スペーサーに蓄積した濁質を容易に剥がすことが可能となり、脱塩装置の安定性が向上する（特許文献１、２）。しかし、流れを反転させるために必要なバルブ数が大幅に増え、イニシャルコストが大幅に増加してしまう。また、バルブに故障が生じた場合、バルブの切り替えを行うことができず、装置の安定性が大きく損なわれてしまう。さらに流れ反転によるスケール物質に対する剥離効果については言及されていない。 Another method is to reverse the flow direction of the water to be treated in the module. According to this method, it becomes possible to easily remove the turbidity accumulated in the raw water spacer, thereby improving the stability of the desalination apparatus (Patent Documents 1 and 2). However, the number of valves required for reversing the flow is significantly increased, resulting in a significant increase in initial cost. In addition, if a valve fails, the valve cannot be switched, and the stability of the device is greatly impaired. Furthermore, no mention is made of the detachment effect on scale material due to flow reversal.
　特許文献３には、Ｆイオン、Ａｌイオン、及びＮａイオン濃度の低い洗浄水を通水してスケールを洗浄する方法が記載されている。この方法では、逆浸透膜処理工程における流量、圧力、水温の値から算出される標準化透過水量（補正透過水量）と、予め設定された初期標準化透過水量との比率が規定値となったときに、洗浄水の通水に切り替える。しかし、この方法では、低下した脱塩装置の性能を十分に回復させることはできないことが判明した。 Patent Document 3 describes a method of washing scale by passing washing water with low concentrations of F ions, Al ions, and Na ions. In this method, when the ratio between the standardized permeate amount (corrected permeate amount) calculated from the values of flow rate, pressure, and water temperature in the reverse osmosis membrane treatment process and the preset initial standardized permeate amount becomes a specified value , switch to flow of washing water. However, it has been found that this method cannot sufficiently recover the degraded performance of the desalting apparatus.
特開２００４－１４１８４６号公報JP 2004-141846 A 特開２００４－２６１７２４号公報JP 2004-261724 A 特開２０２０－１２１２７８号公報Japanese Patent Application Laid-Open No. 2020-121278
　本発明は、上記問題に鑑み、脱塩装置の脱塩性能の低下を防止することができる脱塩装置の運転方法を提供することを課題とする。 In view of the above problems, an object of the present invention is to provide a method of operating a desalting device that can prevent deterioration of the desalting performance of the desalting device.
　本発明の一態様の脱塩装置の運転方法は、第１脱塩装置と第２脱塩装置とを有する脱塩装置の運転方法において、
　第１脱塩装置に被処理水を供給して第１の濃縮水と第１の脱塩水とに分離し、該第１の濃縮水を第２脱塩装置に供給して第２の濃縮水と第２の脱塩水とに分離する通常運転工程と、
　該第２脱塩装置の補正透過水量が低下する前に、第２脱塩装置に第１の濃縮水よりも濃度の低い希薄水を通水する希薄水通水運転工程と
を有する。 A method for operating a desalting device according to one aspect of the present invention is a method for operating a desalting device having a first desalting device and a second desalting device, comprising:
The water to be treated is supplied to the first desalination device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to the second desalination device to obtain the second concentrated water. and a normal operation step of separating into a second demineralized water;
and a dilute water passing operation step of passing dilute water having a concentration lower than that of the first concentrated water through the second desalting device before the corrected permeated water amount of the second desalting device decreases.
　本発明の一態様では、前記第２脱塩装置が複数台並列に設置されており、第１脱塩装置と一部の第２脱塩装置とで前記通常運転工程を行っている間に他の第２脱塩装置で前記希薄水通水運転工程を行う。 In one aspect of the present invention, a plurality of the second desalting devices are installed in parallel, and while the normal operation step is being performed in the first desalting device and some of the second desalting devices, other The dilute water passing operation step is performed in the second desalination unit of the above.
　本発明の一態様の脱塩装置の運転方法は、第１脱塩装置と２台の第２脱塩装置とを有する脱塩装置の運転方法において、
　第１脱塩装置に被処理水を供給して第１の濃縮水と第１の脱塩水とに分離し、該第１の濃縮水を一方の第２脱塩装置に供給して第２の濃縮水と第２の脱塩水とに分離し、他方の第２脱塩装置に第１の濃縮水よりも濃度の低い希薄水を通水する第１通水パターンと、
第１脱塩装置に被処理水を供給して第１の濃縮水と第１の脱塩水とに分離し、該第１の濃縮水を他方の第２脱塩装置に供給して第２の濃縮水と第２の脱塩水とに分離し、一方の第２脱塩装置に第１の濃縮水よりも濃度の低い希薄水を通水する第２通水パターンと、
を交互に行う方法であって、
第１通水パターンと第２通水パターンとの切り替えを３０～１８０分に１回の頻度で行う。 A method for operating a desalting apparatus according to one aspect of the present invention is a method for operating a desalting apparatus having a first desalting apparatus and two second desalting apparatuses, comprising:
The water to be treated is supplied to the first desalting device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to one of the second desalting devices to obtain the second a first water flow pattern in which concentrated water and second desalted water are separated, and dilute water having a concentration lower than that of the first concentrated water is passed through the other second desalination device;
The water to be treated is supplied to the first desalting device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to the other second desalting device to obtain the second a second water flow pattern in which concentrated water and second desalted water are separated, and dilute water having a concentration lower than that of the first concentrated water is passed through one of the second desalting devices;
alternating between
Switching between the first water flow pattern and the second water flow pattern is performed once every 30 to 180 minutes.
　本発明の一態様では、希薄水として溶解塩類濃度が飽和溶解度未満となっている水を用いる。 In one aspect of the present invention, water in which the concentration of dissolved salts is less than the saturated solubility is used as dilute water.
　本発明の一態様では、希薄水として、前記第１脱塩装置又は第１脱塩装置と第２脱塩装置の脱塩水を用いる。 In one aspect of the present invention, the desalinated water of the first desalting device or the first desalting device and the second desalting device is used as diluted water.
　本発明の一態様では、希薄水にスケール防止剤を添加する。 In one aspect of the present invention, a scale inhibitor is added to diluted water.
　本発明の一態様では、前記脱塩装置は、逆浸透膜装置である。 In one aspect of the present invention, the desalination device is a reverse osmosis membrane device.
　本発明の一態様では、希薄水の水温が２５℃以上である。 In one aspect of the present invention, the temperature of the dilute water is 25°C or higher.
　本発明の一態様では、前記第１の濃縮水が、水温２０℃以上、ｐＨ＜６．０、カルシウムイオン濃度：５０～５００ｍｇ／Ｌ、アルミニウムイオン濃度：０．０１～０．５ｍｇ／Ｌ、鉄イオン濃度：０．０１～０．２５ｍｇ／Ｌ、シリカ濃度：５００～１５００ｍｇ／Ｌである。 In one aspect of the present invention, the first concentrated water has a water temperature of 20° C. or higher, a pH of <6.0, a calcium ion concentration of 50 to 500 mg/L, an aluminum ion concentration of 0.01 to 0.5 mg/L, Iron ion concentration: 0.01-0.25 mg/L, silica concentration: 500-1500 mg/L.
　本発明の脱塩装置の運転方法の通常運転工程では、被処理水を第１脱塩装置に通水して第１脱塩水と第１濃縮水とに分離し、第１濃縮水を第２脱塩装置に通水して第２脱塩水と第２濃縮水とに分離する。通常運転工程を行うことによって第２脱塩装置の脱塩性能が実質的に低下する前に、第２脱塩装置に希薄水を通水することにより、第２脱塩装置の脱塩性能低下を防止することができる。 In the normal operation step of the desalination apparatus operating method of the present invention, the water to be treated is passed through the first desalination apparatus to separate the first desalted water and the first concentrated water, and the first concentrated water is separated into the second The water is passed through a desalting device to separate into a second desalted water and a second concentrated water. Decrease in desalination performance of the second desalination device by passing dilute water through the second desalination device before the desalination performance of the second desalination device is substantially degraded by performing the normal operation step can be prevented.
　なお、第２脱塩装置のフラックス回復運転を行う際の希薄水として第１又は第２脱塩装置の脱塩水を用いる態様にあっては、タンク等の付帯設備が不要であり、装置構成が簡易となる。また、第１脱塩装置の透過水という塩類濃度の低い水を希薄水として用いることで、被処理水を希薄水として用いる場合よりも、第２脱塩装置の付着スケールを十分に溶解除去することができる。 In addition, in a mode in which the desalinated water of the first or second desalting device is used as dilute water when performing the flux recovery operation of the second desalting device, ancillary equipment such as a tank is unnecessary, and the device configuration is It becomes simple. In addition, by using the permeated water of the first desalting device, which has a low salt concentration, as the dilute water, the attached scale of the second desalting device is sufficiently dissolved and removed as compared with the case where the water to be treated is used as the dilute water. be able to.
実施の形態に係る脱塩装置の運転方法を説明するフロー図である。FIG. 3 is a flow chart explaining a method of operating the desalination apparatus according to the embodiment; 実施の形態に係る脱塩装置の運転方法を説明するフロー図である。FIG. 3 is a flow chart explaining a method of operating the desalination apparatus according to the embodiment; 実施例の脱塩装置の運転方法を説明するフロー図である。It is a flowchart explaining the operating method of the desalination apparatus of an Example. 実施例の脱塩装置の運転方法を説明するフロー図である。It is a flowchart explaining the operating method of the desalination apparatus of an Example. 実施例及び比較例の結果を示すグラフである。4 is a graph showing the results of Examples and Comparative Examples.
　以下、図１，２を参照して第1の実施の形態について説明する。本実施の形態では、脱塩装置として逆浸透膜装置（ＲＯ装置）を例に挙げて説明するが、本発明はこれに限定されるものではない。なお、逆浸透膜としては芳香族ポリアミド系逆浸透膜が好適であるが、これに限定されない。逆浸透膜装置以外の脱塩装置としては、ナノろ過膜装置、正浸透膜装置、膜蒸留装置、電気透析装置、電気脱イオン装置などが例示される。また、被処理水としては、塩類濃度が１０～５０００ｍｇ／Ｌ特に５０～１０００ｍｇ／Ｌ程度の工業用水、井戸水、フッ素含有排水等が例示されるが、これに限定されない。 The first embodiment will be described below with reference to FIGS. In the present embodiment, a reverse osmosis membrane device (RO device) will be described as an example of a desalting device, but the present invention is not limited to this. As the reverse osmosis membrane, an aromatic polyamide-based reverse osmosis membrane is suitable, but the reverse osmosis membrane is not limited to this. Examples of desalting devices other than reverse osmosis membrane devices include nanofiltration membrane devices, forward osmosis membrane devices, membrane distillation devices, electrodialysis devices, and electrodeionization devices. Examples of the water to be treated include, but are not limited to, industrial water, well water, and fluorine-containing waste water having a salt concentration of about 10 to 5000 mg/L, particularly about 50 to 1000 mg/L.
　図１、２は実施の形態に係る脱塩装置の運転方法に用いられる脱塩装置の構成を示すものである。なお、運転時の水の流れを太実線で示す。図中のＰＩは圧力センサ、ＦＩは流量センサを示す。 FIGS. 1 and 2 show the configuration of a desalting device used in the desalting device operating method according to the embodiment. The thick solid line indicates the flow of water during operation. In the figure, PI indicates a pressure sensor, and FI indicates a flow sensor.
　この実施の形態では、第１ＲＯ装置４と、第２ＲＯ装置とが直列に設置されている。第２ＲＯ装置として、２個の第２ＲＯ装置２１，２２が並列に設置されている。図１では一方の第２ＲＯ装置２１が通常運転し、他方の第２ＲＯ装置２２が希薄水通水運転しており、図２では該一方の第２ＲＯ装置２１が、希薄水通水運転し、該他方の第２ＲＯ装置２２が通常運転している。 In this embodiment, the first RO device 4 and the second RO device are installed in series. As the second RO device, two second RO devices 21 and 22 are installed in parallel. In FIG. 1, one second RO device 21 is in normal operation and the other second RO device 22 is in lean water flow operation, and in FIG. The other second RO device 22 is operating normally.
［図１の運転時］
　図１の通り、原水タンク１内の原水は、ポンプ２、配管３を介して第１ＲＯ装置４に供給され、脱塩水（透過水）が配管３１、バルブ３２、配管３３を介して脱塩水として取り出される。 [During operation in Fig. 1]
As shown in FIG. 1, the raw water in the raw water tank 1 is supplied to the first RO device 4 via the pump 2 and the pipe 3, and the desalinated water (permeated water) is passed through the pipe 31, the valve 32, and the pipe 33 as desalted water. taken out.
　第１ＲＯ装置４の濃縮水（第１濃縮水）は、配管３４、３５、バルブ３６、配管３７を介して一方の第２ＲＯ装置２１に供給される。 The concentrated water (first concentrated water) of the first RO device 4 is supplied to one second RO device 21 via pipes 34 and 35, valve 36, and pipe 37.
　第２ＲＯ装置２１の脱塩水（透過水）は、配管６１、６２を介して前記配管３３に合流し、脱塩水として取り出される。第２ＲＯ装置２１の濃縮水は、配管６３、バルブ６４、配管６５、バルブ６６、配管６７を介して濃縮水として取り出される。 The desalted water (permeated water) of the second RO device 21 joins the pipe 33 via pipes 61 and 62 and is taken out as desalted water. Condensed water in the second RO device 21 is taken out as concentrated water via a pipe 63 , a valve 64 , a pipe 65 , a valve 66 and a pipe 67 .
　配管３４から分岐した配管３８がバルブ３９、配管４０を介して他方の第２脱塩装置２２の給水口に接続されている。図１ではバルブ３９は閉とされている。 A pipe 38 branched from the pipe 34 is connected via a valve 39 and a pipe 40 to the water inlet of the second desalination device 22 on the other side. In FIG. 1 the valve 39 is closed.
　配管３１、３７間が配管４１、バルブ４２によって接続されている。また、前記配管３１、４０間が配管４３、バルブ４４によって接続されている。図１ではバルブ４２は閉、バルブ４４は開とされている。そのため、配管３１の第１脱塩水の一部は、配管４３、４０を介して第２脱塩装置２２の給水口に供給され、第２脱塩装置２２が希薄水通水運転される。 The pipes 31 and 37 are connected by a pipe 41 and a valve 42 . Further, the pipes 31 and 40 are connected by a pipe 43 and a valve 44 . In FIG. 1, valve 42 is closed and valve 44 is open. Therefore, part of the first desalted water in the pipe 31 is supplied to the water supply port of the second desalinator 22 through the pipes 43 and 40, and the second desalinator 22 is operated with dilute water.
　この他方の第２ＲＯ装置２２の希薄水通水運転時には、該他方の第２ＲＯ装置２２の脱塩水は、配管７３、６２を介して配管３３に合流し、脱塩水として取り出される。第２ＲＯ装置２２の濃縮水は、配管７４、７７、バルブ７８、配管７９、７１を介して原水タンク１に返送される。 During the dilute water flow operation of the other second RO device 22, the desalted water of the other second RO device 22 joins the pipe 33 via the pipes 73 and 62 and is taken out as desalted water. The concentrated water from the second RO device 22 is returned to the raw water tank 1 via pipes 74, 77, a valve 78, and pipes 79, 71.
［図２の運転時］
　図１とは逆に、図２では該一方の第２脱塩装置２１が希薄水通水運転し、該他方の第２脱塩装置２２が通常運転している。この場合も、原水タンク１内の原水は、ポンプ２、配管３を介して第１ＲＯ装置４に供給され、脱塩水（透過水）が配管３１、バルブ３２、配管３３を介して脱塩水として取り出される。 [During operation in Fig. 2]
Contrary to FIG. 1, in FIG. 2, one of the second demineralizers 21 is operating with dilute water, and the other second demineralizer 22 is normally operating. In this case also, the raw water in the raw water tank 1 is supplied to the first RO device 4 via the pump 2 and the pipe 3, and the desalinated water (permeated water) is taken out as desalted water via the pipe 31, the valve 32, and the pipe 33. be
　図２では、バルブ３６が閉、バルブ３９が開とされている。そのため、第１ＲＯ装置４の濃縮水（第１濃縮水）は、配管３４、３８、バルブ３９、配管４０を介して他方の第２ＲＯ装置２２に供給される。 In FIG. 2, the valve 36 is closed and the valve 39 is open. Therefore, the concentrated water (first concentrated water) of the first RO device 4 is supplied to the other second RO device 22 via pipes 34 and 38 , valve 39 and pipe 40 .
　第２ＲＯ装置２２の脱塩水（透過水）は、配管７３、６２を介して前記配管３３に合流し、脱塩水として取り出される。第２ＲＯ装置２２の濃縮水は、配管７４、７５，バルブ７６を介して、配管６５に流れ、濃縮水として取り出される。 The desalted water (permeated water) of the second RO device 22 joins the pipe 33 via the pipes 73 and 62 and is taken out as desalted water. Condensed water from the second RO device 22 flows through pipes 74, 75 and valve 76 into pipe 65 and is taken out as concentrated water.
　また、図２ではバルブ４２は開、バルブ４４は閉とされている。そのため、配管３１の第１脱塩水の一部は、配管４２、３７を介して一方の第２脱塩装置２１の給水口に供給され、第２脱塩装置２１が希薄水通水運転される。該一方の第２ＲＯ装置２１の脱塩水は、配管６１、６２を介して配管３３に合流し、脱塩水として取り出される。該一方の第２ＲＯ装置２１の濃縮水は、配管６３、６８、バルブ６９、配管７０、７１を介して原水タンク１に返送される。 Also, in FIG. 2, the valve 42 is open and the valve 44 is closed. Therefore, a part of the first desalted water in the pipe 31 is supplied to the water supply port of one of the second desalting devices 21 through the pipes 42 and 37, and the second desalting device 21 is operated with dilute water. . The desalted water of the one second RO device 21 joins the pipe 33 via the pipes 61 and 62 and is taken out as desalted water. The concentrated water of the one second RO device 21 is returned to the raw water tank 1 via the pipes 63, 68, the valve 69, and the pipes 70, 71.
　このように、図１、２の脱塩装置の運転方法においては、並列設置された２台の第２脱塩装置２１、２２のうち一方で通常運転しながら、他方で第１脱塩水を通水して希薄水通水運転を行うことで、脱塩装置を停止することなく、第２ＲＯ装置の性能低下を防ぐことができる。 1 and 2, one of the two second desalting devices 21 and 22 installed in parallel is normally operated while the other is passing the first desalted water. By performing the dilute water flow operation with water, it is possible to prevent deterioration of the performance of the second RO device without stopping the desalination device.
　図１、２では、第１ＲＯ装置４が１基設置され、第２ＲＯ装置２１、２２が合計２基設置されているが、それ以上ずつ設置されてもよい。また、図１、２では、第２ＲＯ装置２１，２２それぞれが希薄水通水運転しているときには、希薄水は濃縮水と脱塩水とに分離されているが、脱塩水流路のバルブ（図示せず）を閉じることで希薄水は濃縮水と脱塩水とに分離せず、第２ＲＯ装置２１，２２からは濃縮水のみを排出するようにしても良い。 1 and 2, one first RO device 4 is installed and a total of two second RO devices 21 and 22 are installed, but more may be installed each. In FIGS. 1 and 2, when the second RO devices 21 and 22 are in the diluted water flow operation, the diluted water is separated into concentrated water and desalinated water. (not shown) may be closed so that the diluted water is not separated into concentrated water and desalted water, and only the concentrated water is discharged from the second RO devices 21 and 22 .
［希薄水の通水速度］
　希薄水の通水速度は、脱塩装置の閉塞状態に応じて適宜決定することができるが、例えば逆浸透膜の場合、０．００１～１ｍ／ｓ、特に０．０２～０．２ｍ／ｓが好ましい。具体的には、４インチモジュールでは１本あたり３００～２０００Ｌ／Ｈｒであることが好ましく、８インチモジュールでは１本あたり１．８～１０ｍ３／Ｈｒであることが好ましい。また、脱塩装置の濃縮水排出側での圧力は０．１～２ＭＰａであることが好ましい。 [Flow rate of dilute water]
The flow rate of dilute water can be appropriately determined according to the clogging state of the desalting device. is preferred. Specifically, it is preferably 300 to 2000 L/Hr per one 4-inch module, and 1.8 to 10 m 3 /Hr per one 8-inch module. Further, the pressure on the concentrated water discharge side of the desalting device is preferably 0.1 to 2 MPa.
［希薄水を通水する第２脱塩装置の切り替えタイミング］
　第２ＲＯ装置の補正透過フラックスが運転初期から低下する前に、具体的には運転初期から５％以上低下するよりも前に、希薄水を通水する第２ＲＯ装置を切り替える。なお、この５％は一例であり、１～５％の間から選択された値であればよい。特に、第２ＲＯ装置において最も濃縮のかかる末端ＲＯの透過フラックスの変化を測定することが好ましい。補正透過フラックスは、後述の実施例に記載の通りである。 [Switching timing of the second desalination device through which dilute water is passed]
Before the corrected permeation flux of the second RO device drops from the initial stage of operation, specifically before it drops by 5% or more from the initial stage of operation, the second RO device through which lean water is passed is switched. Note that this 5% is just an example, and any value selected from between 1 and 5% may be used. In particular, it is preferable to measure the change in permeation flux of the most concentrated terminal RO in the second RO device. The corrected transmission flux is as described in the examples below.
　補正透過フラックスの減少量を検知するのではなく、所定時間、一方の第２ＲＯ装置を所定時間通常運転し他方の第２ＲＯ装置を希薄水通水運転した後に、該一方の第２ＲＯ装置を通常運転とし該他方の第２ＲＯ装置を希薄水通水運転に切り替えることも可能である。この所定時間としては、１０～２４０分、特に３０～１８０分、例えば約９０分が例示される。 Instead of detecting the amount of decrease in the corrected permeated flux, one of the second RO devices is normally operated for a predetermined period of time and the other second RO device is operated with lean water, and then the one of the second RO devices is operated normally. However, it is also possible to switch the other second RO device to lean water flow operation. This predetermined time is exemplified by 10 to 240 minutes, especially 30 to 180 minutes, eg about 90 minutes.
［希薄水の水質］
　上記実施の形態では、希薄水として第１脱塩水を用いているが、本発明では、希薄水は、溶解塩類が飽和溶解度未満となっていればよい。したがって、第２脱塩水（第２ＲＯ装置の透過水）を希薄水として用いてもよい。また、第１ＲＯ装置または第２ＲＯ装置の透過水と原水とを混合したものを希薄水として用いてもよい。更には第１ＲＯ装置または第２ＲＯ装置の透過水と第１濃縮水とを混合したものを希薄水として用いてもよい。溶解塩類の飽和溶解度とは、Ｘ＋のモル濃度［Ｘ＋］及びＹ－のモル濃度［Ｙ－］に関してスケール種ＸＹの溶解度積Ｋｓｐについて、［Ｘ＋］［Ｙ－］＝Ｋｓｐを満たすものである。 [Quality of dilute water]
In the above embodiment, the first desalted water is used as the dilute water, but in the present invention, the dissolved salts in the dilute water should be less than the saturation solubility. Therefore, the second desalted water (permeated water of the second RO device) may be used as diluted water. Further, a mixture of the permeated water of the first RO device or the second RO device and raw water may be used as diluted water. Furthermore, a mixture of the permeated water of the first RO device or the second RO device and the first concentrated water may be used as diluted water. The saturated solubility of a dissolved salt satisfies [X + ][Y − ]=Ksp for the solubility product Ksp of scale type XY with respect to the molar concentration of X + [X + ] and the molar concentration of Y − [ Y − ]. is.
　なお、希薄水の水温が低い場合は透過水量の回復効果は小さいため、希薄水の水温は２０℃以上特に２５℃以上であることが好ましい。 When the temperature of the dilute water is low, the effect of recovering the amount of permeated water is small.
［希薄水に添加するスケール防止剤］
　希薄水にはスケール防止剤を添加してもよい。スケール防止剤を添加することでスケールの溶解力の向上および溶解したスケールの再付着防止という効果を得ることができる。 [Scale inhibitor added to dilute water]
A scale inhibitor may be added to the dilute water. By adding a scale inhibitor, it is possible to obtain the effects of improving the dissolving power of scale and preventing reattachment of dissolved scale.
　スケール防止剤は、用いる脱塩装置の種類や原水によって適宜選択することができる。脱塩装置として逆浸透膜装置を用い、炭酸カルシウムスケールが生成するような被処理水の場合には、２－ホスホノブタン－１，２，４－トリカルボン酸等のホスホン酸やアクリル酸と２―アクリルアミド－２－メチルプロパンスルホン酸の共重合ポリマー、ポリアクリル酸などを用いることができ、フッ化カルシウムスケールが生成するような被処理水の場合には、２－ホスホノブタン－１，２，４－トリカルボン酸等のホスホン酸、ポリアクリル酸などを用いることができる。また、これらスケール防止剤の添加量は１０～１０００ｍｇ／Ｌ程度である。 The scale inhibitor can be appropriately selected according to the type of desalination equipment used and the raw water. A reverse osmosis membrane device is used as a desalination device, and in the case of water to be treated that produces calcium carbonate scale, phosphonic acid such as 2-phosphonobutane-1,2,4-tricarboxylic acid, acrylic acid and 2-acrylamide -Copolymer of 2-methylpropanesulfonic acid, polyacrylic acid, etc. can be used, and in the case of water to be treated that produces calcium fluoride scale, 2-phosphonobutane-1,2,4-tricarboxylic acid Phosphonic acid such as acid, polyacrylic acid, and the like can be used. The amount of these scale inhibitors added is about 10 to 1000 mg/L.
　なお、希薄水にｐＨ調整剤を添加し、スケールの溶解力の向上および溶解したスケールの再付着防止という効果を得るようにしてもよい。 It should be noted that a pH adjuster may be added to the dilute water to obtain the effects of improving the dissolving power of scale and preventing reattachment of dissolved scale.
［希薄水の通水方向］
　図１のように希薄水を通水する場合は、第２ＲＯ装置の給水側から通水するのが好ましいが、第２ＲＯ装置の濃縮水出口側から通水しても構わない。また希薄水を通水している間は、脱塩装置の濃縮水が飽和溶解度未満の範囲内で回収率を維持し、処理水を生産しながら通水しても構わない。 [Direction of flow of dilute water]
When dilute water is passed through as shown in FIG. 1, it is preferable to pass through the water supply side of the second RO device, but water may be passed through the concentrated water outlet side of the second RO device. In addition, while dilute water is being passed through, the recovery rate of concentrated water from the demineralizer may be maintained within the range of less than the saturated solubility, and water may be passed while producing treated water.
　上記実施の形態では、ＲＯ装置が２段に設置されているが、３段以上に設置されてもよい。なお、３段以上に設置した場合には、希薄水を通水する脱塩装置は最後段のものとすることが好ましい。 Although the RO devices are installed in two stages in the above embodiment, they may be installed in three or more stages. When three or more stages are installed, it is preferable that the desalinator through which dilute water is passed is the one at the last stage.
［第１濃縮水の水質］
　本発明は、第２ＲＯ装置でフッ化カルシウムスケールまたは炭酸カルシウムスケールが生成する場合に好適に用いることができる。具体的には、第２ＲＯ装置に供給される第１濃縮水が以下の場合に好適に用いることができる。
水温２０℃以上
ｐＨ＜６．０
カルシウムイオン濃度：５０～５００ｍｇ／Ｌ（好ましくは１００～２５０ｍｇ／Ｌ）
アルミニウムイオン濃度：０．０１～０．５ｍｇ／Ｌ（好ましくは０．１～０．２５ｍｇ／Ｌ）
鉄イオン濃度：０．０１～０．２５ｍｇ／Ｌ（好ましくは０．１～０．２５ｍｇ／Ｌ）
シリカ濃度：５００～１５００ｍｇ／Ｌ（好ましくは７００～１２００ｍｇ／Ｌ） [Quality of first concentrated water]
The present invention can be suitably used when calcium fluoride scale or calcium carbonate scale is generated in the second RO device. Specifically, the first concentrated water supplied to the second RO device can be suitably used in the following cases.
Water temperature 20°C or higher pH < 6.0
Calcium ion concentration: 50-500 mg/L (preferably 100-250 mg/L)
Aluminum ion concentration: 0.01 to 0.5 mg/L (preferably 0.1 to 0.25 mg/L)
Iron ion concentration: 0.01 to 0.25 mg/L (preferably 0.1 to 0.25 mg/L)
Silica concentration: 500-1500 mg/L (preferably 700-1200 mg/L)
　図３，４に示す試験装置を用いて模擬原水の処理運転（図３）及び第２ＲＯ装置への希薄水通水運転（図４）を交互に行った。なお、本試験では、フラックス値として補正透過フラックス値を用いる。 Using the test equipment shown in Figures 3 and 4, the simulated raw water treatment operation (Figure 3) and the dilute water flow operation to the second RO device (Figure 4) were alternately performed. In addition, in this test, the corrected permeation flux value is used as the flux value.
［補正透過フラックス］
　実際の透過フラックスは、運転圧力、水温、給水中の塩類濃度の影響を受けるため、ＲО装置の性能を示すデータとして補正透過フラックスで規定することが望ましい。 [Corrected transmission flux]
Since the actual permeation flux is affected by the operating pressure, water temperature, and salt concentration in the feed water, it is desirable to specify the corrected permeation flux as data indicating the performance of the RO device.
　ここで、補正透過フラックスはＪＩＳ　Ｋ　３８０２１９９０に示されるような逆浸透膜エレメント及びモジュール透過水量性能データの標準化方法に記載の方法で算出することが一般的である。 Here, the corrected permeation flux is generally calculated by the method described in the method for standardizing permeation water amount performance data of reverse osmosis membrane elements and modules as shown in JIS K 38021990.
　すなわち、透過水量性能データは以下の式（１）によって補正することで、補正透過フラックスFpsとして算出する。 That is, the water permeation performance data is corrected by the following formula (1) to calculate the corrected permeation flux Fps .
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
　ここで、Ｑｐａ：実運転条件での透過水量（ｍ３／ｄ）
　　　　　Ｐｆａ：実運転条件での操作圧力（ｋＰａ）
　　　　　ΔＰｆｂａ：実運転条件でのモジュール差圧（ｋＰａ）
　　　　　Ｐｐａ：実運転条件での透過水側の圧力（ｋＰａ）
　　　　　Πｆｂａ：実運転条件での供給側、濃縮側の平均溶質濃度の浸透圧（ｋＰａ）
　　　　　ＴＣＦａ：実運転条件での温度換算係数
　　　　　Ｐｆｓ：標準運転条件での操作圧力（ｋＰａ）
　　　　　ΔＰｆｂｓ：標準運転条件でのモジュール差圧（ｋＰａ）
　　　　　Ｐｐｓ：標準運転条件での透過水側の圧力（ｋＰａ）
　　　　　Πｆｂｓ：標準運転条件での供給側、濃縮側の平均溶質濃度の浸透圧（ｋＰａ）
　　　　　ＴＣＦｓ：標準運転条件での温度換算係数 Here, Q pa : amount of permeated water under actual operating conditions (m 3 /d)
P fa : Operating pressure (kPa) under actual operating conditions
ΔP fba : Module differential pressure (kPa) under actual operating conditions
P pa : Permeate side pressure (kPa) under actual operating conditions
Π fba : Osmotic pressure (kPa) of the average solute concentration on the supply side and concentration side under actual operating conditions
TCF a : Temperature conversion factor under actual operating conditions P fs : Operating pressure under standard operating conditions (kPa)
ΔP fbs : Module differential pressure (kPa) under standard operating conditions
P ps : Permeate side pressure (kPa) under standard operating conditions
Π fbs : Osmotic pressure (kPa) of average solute concentration on feed side and concentration side under standard operating conditions
TCF s : Temperature conversion factor under standard operating conditions
＜図３，４の脱塩装置の構成＞
　原水タンク８１内の原水が、ポンプ８２、配管８３を介して送水可能とされている。配管８３は配管８４，８５に分岐し、第１ＲＯ装置８６，８７に接続されている。第１ＲＯ装置８６，８７の透過水は、配管８８，８９及び合流配管９０を介して脱塩水として取り出し可能とされている。 <Structure of Desalting Apparatus in FIGS. 3 and 4>
Raw water in a raw water tank 81 can be sent through a pump 82 and a pipe 83 . The pipe 83 branches into pipes 84 and 85 and is connected to first RO devices 86 and 87 . Permeated water from the first RO devices 86 and 87 can be taken out as demineralized water via pipes 88 and 89 and a confluence pipe 90 .
　第１ＲＯ装置８６，８７の濃縮水は、配管９１，９２及び合流配管９３を介して第２ＲＯ装置９４に供給される。第２ＲＯ装置９４の透過水は、配管９５から配管９０に合流する。第２ＲＯ装置９４の濃縮水は、配管９６を介して系外に排出される。 The concentrated water from the first RO devices 86 and 87 is supplied to the second RO device 94 via the pipes 91 and 92 and the confluence pipe 93. The permeated water of the second RO device 94 joins the pipe 90 from the pipe 95 . Condensed water in the second RO device 94 is discharged outside the system through a pipe 96 .
　希薄水タンク９７内の希薄水がポンプ９８、配管９９及び前記配管９３を介して第２ＲＯ装置９４に供給可能とされている。この試験例では、希薄水として上記脱塩水を用いる。 The dilute water in the dilute water tank 97 can be supplied to the second RO device 94 via the pump 98, the pipe 99 and the pipe 93. In this test example, the above desalted water is used as diluted water.
　図３は、通常の原水処理運転状態を示しており、ポンプ８２が作動し、ポンプ９８は停止している。原水は、第１ＲＯ装置８６，８７あるいはさらに第２ＲＯ装置９４でＲＯ処理され、透過水（脱塩水）と濃縮水とに分離される。 　Fig. 3 shows a normal raw water treatment operating state, in which the pump 82 is operating and the pump 98 is stopped. The raw water is subjected to RO treatment by the first RO devices 86, 87 or the second RO device 94, and separated into permeated water (demineralized water) and concentrated water.
　図４は、第２ＲＯ装置９４に希薄水を通水している状態を示している。図４では、ポンプ８２を停止し、ポンプ９８のみを作動させ、第１ＲＯ装置８６，８７への原水供給を停止している。第２ＲＯ装置９４に希薄水タンク９８内の希薄水が通水されることにより、第２ＲＯ装置９４のスケールが溶解除去される。 FIG. 4 shows a state in which dilute water is passed through the second RO device 94 . In FIG. 4, the pump 82 is stopped, only the pump 98 is operated, and the raw water supply to the first RO devices 86 and 87 is stopped. The dilute water in the dilute water tank 98 is passed through the second RO device 94 to dissolve and remove the scale of the second RO device 94 .
　なお、図４では、第２ＲＯ装置９４に希薄水を通水しているときに透過水を配管９５に流出させないようにしているが、第２ＲＯ装置９４に希薄水を通水しているときに透過水を配管９５に流出させるようにしてもよい。 In FIG. 4, the permeated water is prevented from flowing out to the pipe 95 when dilute water is passed through the second RO device 94. However, when dilute water is passed through the second RO device 94, The permeated water may be allowed to flow out to the pipe 95 .
＜模擬原水＞
模擬原水として、塩化カルシウム(１１０ｍｇ／Ｌ)、炭酸水素ナトリウム(７０ｍｇ／Ｌ)、メタケイ酸ナトリウム（１６１０ｍｇ／Ｌ）、塩化アルミニウム６水和物（０．４５ｍｇ／Ｌ）、塩化第二鉄（０．４ｍｇ／Ｌ）、スケール防止剤（２－ホスホノブタン－１，２，４－トリカルボン酸）（１０ｍｇ／Ｌ）を含有する水溶液を調製し、更に、水酸化ナトリウム水溶液又は硫酸水溶液でｐＨを５．５に調整したもの（水温２０℃）を用いた。 <Simulated raw water>
As simulated raw water, calcium chloride (110 mg/L), sodium hydrogen carbonate (70 mg/L), sodium metasilicate (1610 mg/L), aluminum chloride hexahydrate (0.45 mg/L), ferric chloride (0 .4 mg/L) and a scale inhibitor (2-phosphonobutane-1,2,4-tricarboxylic acid) (10 mg/L) were prepared, and further adjusted to pH 5.0 with an aqueous sodium hydroxide solution or an aqueous sulfuric acid solution. 5 (water temperature 20° C.) was used.
＜希薄水＞
　希薄水として、模擬原水を図３のようにＲＯ装置に通水したときの透過水を用いた。なお、上記スケール防止剤を１０ｍｇ／Ｌ添加した。 <Diluted water>
As diluted water, permeate water obtained by passing simulated raw water through an RO apparatus as shown in FIG. 3 was used. In addition, 10 mg/L of the above scale inhibitor was added.
［実施例１］
　図３，４の脱塩装置に、上記模擬原水と模擬希薄水とを次の順序及び条件で通水した。 [Example 1]
The simulated raw water and simulated dilute water were passed through the desalting apparatus shown in FIGS. 3 and 4 in the following order and under the following conditions.
＜通水順序＞
　模擬原水通水工程（図３）：模擬原水を初期透過フラックス０．４５ｍ／Ｄ、通水流速０．１ｍ／ｓとなるように通水し、回収率７３％で運転を９０分行った。（補正透過フラックスは、運転９０分では、実質的には低下しない。）
希薄水通水工程（図４）：模擬原水通水工程を９０分行った後に、希薄水を模擬原水通水工程と同一の圧力、通水量にて３０分通水する。その後、図３の模擬原水通水工程に戻る。 <Water flow order>
Simulated raw water flow process (Fig. 3): Simulated raw water was passed so that the initial permeation flux was 0.45 m/D and the water flow rate was 0.1 m/s, and the operation was carried out for 90 minutes at a recovery rate of 73%. (Corrected permeate flux does not drop substantially at 90 minutes of operation.)
Dilute water flow process (Fig. 4): After performing the simulated raw water flow process for 90 minutes, dilute water is passed for 30 minutes at the same pressure and water flow rate as the simulated raw water flow process. After that, the process returns to the simulated raw water passing step in FIG.
［比較例１］
　図３の模擬原水通水工程において、フラックスと初期標準化透過水量との比率が９０％となったときに、図４の希薄水の通水（３０分通水）に切り替えるようにしたこと以外は実施例１と同様にして図３の模擬原水通水及び図４の希薄水通水を交互に行った。 [Comparative Example 1]
Except that in the simulated raw water flow process of FIG. In the same manner as in Example 1, simulated raw water flow in FIG. 3 and dilute water flow in FIG. 4 were alternately performed.
［結果及び考察］
　模擬原水通水工程終了直前における第２ＲＯ装置９４のフラックスＦと初期フラックスＦ０との比Ｆ／Ｆ０を「補正透過水量比」として図５に示す。図５の通り、実施例１のように、ＲＯ膜のフラックスが低下する前に希薄水通水工程を行うことにより、ＲＯ膜の性能低下を防ぐことが可能となる。これに対し、フラックスと初期標準化透過水量との比率が９０％となったときに、希薄水の通水に切り替えるようにした場合には、性能低下した脱塩装置の性能を十分に回復させることはできない（比較例１）。 [Results and discussion]
The ratio F/ F0 between the flux F of the second RO device 94 and the initial flux F0 immediately before the simulated raw water passing step is completed is shown in FIG. As shown in FIG. 5, performance degradation of the RO membrane can be prevented by performing the dilute water passing step before the flux of the RO membrane decreases, as in Example 1. FIG. On the other hand, when the ratio of the flux to the initial standardized permeate amount reaches 90%, when the flow of dilute water is switched to, the performance of the desalinator, which has deteriorated, can be fully recovered. (Comparative Example 1).
　本発明を特定の態様を用いて詳細に説明したが、本発明の意図と範囲を離れることなく様々な変更が可能であることは当業者に明らかである。
　本出願は、２０２２年３月３日付で出願された日本特許出願２０２２－０３２７５５に基づいており、その全体が引用により援用される。 Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application 2022-032755 filed on March 3, 2022, which is incorporated by reference in its entirety.
　１　原水タンク
　４　第１ＲＯ装置
　２１，２２　第２ＲＯ装置
　８１　原水タンク
　８６，８７　第１ＲＯ装置
　９４　第２ＲＯ装置
　９７　希薄水タンク 1 raw water tank 4 first RO device 21, 22 second RO device 81 raw water tank 86, 87 first RO device 94 second RO device 97 dilute water tank

Claims (9)

  1. 　第１脱塩装置と第２脱塩装置とを有する脱塩装置の運転方法において、
    　第１脱塩装置に被処理水を供給して第１の濃縮水と第１の脱塩水とに分離し、該第１の濃縮水を第２脱塩装置に供給して第２の濃縮水と第２の脱塩水とに分離する通常運転工程と、
    　該第２脱塩装置の補正透過水量が低下する前に、第２脱塩装置に第１の濃縮水よりも濃度の低い希薄水を通水する希薄水通水運転工程と
    を有することを特徴とする脱塩装置の運転方法。     In a method for operating a desalting device having a first desalting device and a second desalting device,
    The water to be treated is supplied to the first desalination device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to the second desalination device to obtain the second concentrated water. and a normal operation step of separating into a second demineralized water;
    and a dilute water passing operation step of passing dilute water having a concentration lower than that of the first concentrated water through the second desalting device before the corrected permeated water amount of the second desalting device decreases. A method of operating a desalination device.
  2. 　前記第２脱塩装置が複数台並列に設置されており、第１脱塩装置と一部の第２脱塩装置とで前記通常運転工程を行っている間に他の第２脱塩装置で前記希薄水通水運転工程を行う請求項１の脱塩装置の運転方法。 A plurality of the second desalination devices are installed in parallel, and while the normal operation process is being performed in the first desalination device and some of the second desalination devices, the other second desalination devices 2. The method of operating a desalting apparatus according to claim 1, wherein said dilute water passing operation step is performed.
  3. 　第１脱塩装置と２台の第２脱塩装置とを有する脱塩装置の運転方法において、
    　第１脱塩装置に被処理水を供給して第１の濃縮水と第１の脱塩水とに分離し、該第１の濃縮水を一方の第２脱塩装置に供給して第２の濃縮水と第２の脱塩水とに分離し、他方の第２脱塩装置に第１の濃縮水よりも濃度の低い希薄水を通水する第１通水パターンと、
    第１脱塩装置に被処理水を供給して第１の濃縮水と第１の脱塩水とに分離し、該第１の濃縮水を他方の第２脱塩装置に供給して第２の濃縮水と第２の脱塩水とに分離し、一方の第２脱塩装置に第１の濃縮水よりも濃度の低い希薄水を通水する第２通水パターンと、
    を交互に行う方法であって、
    第１通水パターンと第２通水パターンとの切り替えを３０～１８０分に１回の頻度で行う請求項１の脱塩装置の運転方法。     In a method for operating a desalting device having a first desalting device and two second desalting devices,
    The water to be treated is supplied to the first desalting device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to one of the second desalting devices to obtain the second a first water flow pattern in which concentrated water and second desalted water are separated, and dilute water having a concentration lower than that of the first concentrated water is passed through the other second desalination device;
    The water to be treated is supplied to the first desalting device and separated into the first concentrated water and the first desalted water, and the first concentrated water is supplied to the other second desalting device to obtain the second a second water flow pattern in which concentrated water and second desalted water are separated, and dilute water having a concentration lower than that of the first concentrated water is passed through one of the second desalting devices;
    alternating between
    2. The method of operating a desalination apparatus according to claim 1, wherein switching between the first water flow pattern and the second water flow pattern is performed once every 30 to 180 minutes.
  4. 　希薄水として溶解塩類濃度が飽和溶解度未満となっている水を用いる、請求項１～３のいずれかの脱塩装置の運転方法。 The method of operating a desalination apparatus according to any one of claims 1 to 3, wherein water having a concentration of dissolved salts less than the saturation solubility is used as dilute water.
  5. 　希薄水として、前記第１脱塩装置又は第１脱塩装置と第２脱塩装置の脱塩水を用いる、請求項１～３のいずれかの脱塩装置の運転方法。 The method of operating a desalination device according to any one of claims 1 to 3, wherein the desalinated water of the first desalination device or the first desalination device and the second desalination device is used as the dilute water.
  6. 　希薄水にスケール防止剤を添加する、請求項１～５のいずれかの脱塩装置の運転方法。 The method of operating a desalination apparatus according to any one of claims 1 to 5, wherein a scale inhibitor is added to the dilute water.
  7. 　前記脱塩装置は、逆浸透膜装置である、請求項１～６のいずれかの脱塩装置の運転方法。 The method of operating a desalting device according to any one of claims 1 to 6, wherein the desalting device is a reverse osmosis membrane device.
  8. 　希薄水の水温が２５℃以上である、請求項１～７のいずれかの脱塩装置の運転方法。 The method of operating a desalination apparatus according to any one of claims 1 to 7, wherein the dilute water has a temperature of 25°C or higher.
  9. 　前記第１の濃縮水が、水温２０℃以上、ｐＨ＜６．０、カルシウムイオン濃度：５０～５００ｍｇ／Ｌ、アルミニウムイオン濃度：０．０１～０．５ｍｇ／Ｌ、鉄イオン濃度：０．０１～０．２５ｍｇ／Ｌ、シリカ濃度：５００～１５００ｍｇ／Ｌである請求項１～８のいずれかの脱塩装置の運転方法。 The first concentrated water has a water temperature of 20° C. or higher, pH < 6.0, calcium ion concentration: 50 to 500 mg / L, aluminum ion concentration: 0.01 to 0.5 mg / L, iron ion concentration: 0.01. 9. The method for operating a desalting apparatus according to any one of claims 1 to 8, wherein the silica concentration is 500 to 1500 mg/L and the silica concentration is 0.25 mg/L to 0.25 mg/L.
PCT/JP2023/003390 2022-03-03 2023-02-02 Method for operating desalting device WO2023166905A1 (en)

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